Map types

Map types are specified by the type argument in basemap() function. The list below shows all currently implemented map types.

library(PlotSvalbard)
basemap("svalbard")
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons

basemap("kongsfjorden") # or just basemap()

basemap("kongsfjordbotn")

basemap("kronebreen")

basemap("mosj")
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons

basemap("barentssea")

basemap("barentssea", limits = c(12, 24, 68, 71))

Limiting (zooming) the maps

Any basemap can be limited (or zoomed in) using the limits argument. The limits argument has to be a numeric vector specifying the minimum longitude, maximum longitude, minimum latitude and maximum latitude of the limiting area in decimal degrees. The order and length (4) of the vector is rigid.

Note that some map types are already limited, so if you are looking for a map of Kongsfjorden, using basemap("kongsfjorden") might be just what you need.

Adding data to basemaps

Data can be added to basemaps using the + operator and layers for ggplot2. Below you find some examples on how to add your research data on basemaps.

data("npi_stations")

basemap("svalbard", limits = c(3,24,78.5,82), round.lat = 1, round.lon = 2, border.col.land = "#a9750d", border.col.glacier = "grey95") + geom_text(data = npi_stations, aes(x = lon.utm, y = lat.utm, label = Station), color = "red", fontface = 2)
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons

data("kongsfjord_moorings")

basemap("kongsfjorden", limits = c(11.3, 12.69, 78.85, 79.1), round.lat = 0.05, round.lon = 0.5) + geom_text(data = kongsfjord_moorings, aes(x = lon.utm, y = lat.utm, label = Mooring.name, color = Name), fontface = 2, size = 25.4/72.27*8) # font size = 8, see Graphical parameters

data(zooplankton)

x <- cbind(transform_coord(zooplankton, lon = "Longitude", lat = "Latitude"), zooplankton)
#> projection transformed from +proj=longlat +datum=WGS84 to +init=epsg:32633

species <- colnames(x)[!colnames(x) %in% c("lon.utm", "lat.utm", "ID", "Longitude", "Latitude", "Total")]

library(scatterpie)

basemap("barentssea", limits = c(4, 24, 79.5, 83.5), round.lon = 2, round.lat = 1) + geom_scatterpie(aes(x = lon.utm, y = lat.utm, group = ID, r = 100*Total), data = x, cols = species, size = 0.1) + scale_fill_discrete(name = "Species", breaks = species, labels = parse(text = paste0("italic(" , sub("*\\.", "~", species), ")")))

data("chlorophyll")

x <- interpolate(chlorophyll, Subset = "From <= 10", value = "Chla") ## Interpolate
#> [inverse distance weighted interpolation]
plot(x, type = "kongsfjorden", limits = c(11.4,12.7,78.855,79.05), legend.label = "Chlorophyll-a\n(mg/m3)") 

Bathymetry

Not implemented yet, but the feature is planned.

Graphical parameters

The line widths and general looks of the basemaps are optimized for a half page sized pdf figure in scientific journals (Springer figure dimensions were used to develop the function). The line widths may not look good when printed on other devices. You can modify the line widths and colors using size.* and border.col.* arguments.

basemap("svalbard", size.land = 0.01, size.glacier = 0.05, size.grid = 0.05, border.col.glacier = "#52bfe4", border.col.land = "#a9750d")
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons

Approach to remove borders of land and glacier shapes:

basemap("kongsfjorden", border.col.glacier = "grey95", border.col.land = "#eeeac4")

The line width of ggplot2 is 2.13 wider than the line widths measured as points (pt). This means that if you want a certain line width, multiply the desired line width by $1/2.13$ inside size.* arguments. Similar conversion factor for font size is $1/2.845276$.

Performance

The basemap("svalbard") is currently fairly slow (approx. 25 seconds) due to a large size of the shapefiles that are used to generate the map. Unfortunately this slowness also applies for zoomed in maps, because I have not found a way to clip the glacier shapefile. The clip_shapefile function was developed for this purpose, and worked well for land shapes. However, clipping a glacier shapefile takes longer than directly plotting it. It is possible that there is a way to speed up the basemap("svalbard"), but in the current version plotting Svalbard is just slow.

If you are looking for optimal limits for your data, you can use the basemap("barentssea") option to find these limits and replace "barentssea" with "svalbard" once you are done:

system.time(basemap("barentssea", limits = c(c(19.5,23.5,80,81.7))))
#>    user  system elapsed 
#>   0.164   0.005   0.169
system.time(basemap("svalbard", limits = c(c(19.5,23.5,80,81.7))))
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#> Regions defined for each Polygons
#>    user  system elapsed 
#>  23.473   1.723  25.417